DESCRIPTION: The nucleus accumbens has traditionally been implicated in the control of motivation. Preliminary studies have demonstrated that the activation of GABA receptors within the rostral half of the medial accumbens shell increases appetitive motivation (feeding) while activation of GABA receptors in the caudal third of the medial shell increases defensive motivation (defensive treading behavior). The purpose of the proposed experiments is to examine the anatomical processing (anatomical sites and efferent structures) and psychological characteristics (affective and rewarding properties) involved in appetitive behavior elicited from rostral shell sites versus defensive behavior elicited from caudal shell sites. Specifically, we hypothesize that 1) the precise anatomical sites and efferent structures involved in encoding accumbens shell GABA-elicited appetitive versus defensive behavior will be segregated, as assessed by immediate early gene expression, and 2) GABA-mediated appetitive motivation from rostral sites will be accompanied by enhanced positive psychological properties while GABA-mediated defensive motivation from caudal sites will be accompanied by psychologically negative characteristics, as assessed through affective taste reactions and conditioned place preference/avoidance. These experiments will provide more insight into the psychological and anatomical processing of appetitive versus defensive behavior controlled by the nucleus accumbens.